Gen 3 won’t connect to wifi

Using Ubiquiti APs in home environment. No matter what Gen 3 only connects to 2.4 ghz. Ideally would like it to use 5 ghz band, but doesn’t. Unifi AC Pro Gen 2 access point located within 10-15 feet of the Rachio Gen 3 unit. Using iOS 13 iPhone XS Max to connect. How do you get Gen 3 to use 5 ghz band?